The present invention relates generally to diagnostic imaging systems containing a rotating anode X-ray tube. More particularly, the present invention relates to a non-rusting and non-particulating imaging tube rotor assembly and to a method for forming the same.
Various diagnostic imaging X-ray tube systems are presently used, each of which have different system functionality requirements. Because of the different functionality requirements, internal system components vary depending upon the application, the manufacturer, and the system model.
The imaging system includes an X-ray tube that contains an electric motor assembly for rotating an anode. The motor assembly generates a magnetic field that causes an X-ray tube rotor assembly, which is coupled to the anode, to rotate. In order for the X-ray tube to operate properly, the inside of the X-ray tube needs to be free of rust and particulate. Rust can directly and negatively affect rotating efficiency and emissitivity of the X-ray tube as well as create particulate, which may indirectly and also negatively affect X-ray tube operation. Particulate can also be created by spalling of coatings or layers on various X-ray tube components. Particulate within the X-ray tube not only negatively affects rotating efficiency and emissitivity like rust, but also may negatively affect other X-ray tube operation parameters, such as for example, X-ray production, which can degrade image quality. Rust and flaking may occur early in the production and use of an X-ray tube or may occur over time and usage of the X-ray tube.
A large amount of heat is generated within the X-ray tube. In order to dissipate the heat, a coating, having a high emissitivity value, is used over an exterior surface of the X-ray tube rotor assembly. The coating prevents degradation of X-ray tube components by radiating away the heat. Unfortunately, the coating layer tends to flake off over time and form more particulate, which further decreases the performance of the X-ray tube.
Traditionally, X-ray tube rotor assemblies are fabricated from a combination of copper, copper alloy, aluminum, and magnetic steel, or less frequently from a combination of copper, copper alloy, and aluminum. The magnetic steel forms a rotor core. The copper forms a conductive exterior surface on the rotor core. The magnetic steel is the conventional material of choice for the rotor core, due to its magnetic properties and consequential ability to produce electromagnetic torque.
An undesired result of oxidation and rusting has been encountered in production of the X-ray tube rotor assemblies that contain a steel core. The encountered rust is painstaking and costly to prevent and remove from the X-ray tube rotor assemblies.
Two types of X-ray tube rotor assembly design styles that are typically used include a “sheet” design and a “squirrel cage” design. The sheet design includes a copper, a copper alloy, or aluminum conductive sheet formed over a magnetic steel core. The squirrel cage design includes a steel core having integrally formed slots containing copper, copper alloy, or aluminum bars formed therein. Such bars may be exposed on the X-ray tube rotor assembly exterior surface or may be enclosed by the exterior surface of the rotor core. The bars are integrally formed along with a first end cap and a second end cap to form a single component. The squirrel cage design directs current along the bars between the two end caps, which allows for increased current flow, fewer power losses, and increased torque production over the sheet design. The use of either the sheet design or the squirrel cage design depends upon application requirements.
X-ray tube rotor assemblies of both the sheet design and the squirrel cage design have several associated disadvantages. Both designs have the propensity to develop rust over time, thereby generating particulate. Also, both designs have surfaces of low emissitivity, when left uncoated.
Therefore, it would be desirable to provide an improved apparatus and method for preventing generation of particulate within an X-ray tube.